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<H1>set(+Tree0, ++Key, ?Value, -Tree)</H1>
Update the value corresponding to a key in a tree, inserting the key if it doesn't exist already.
<DL>
<DT><EM>Tree0</EM></DT>
<DD>A 2-3-4 tree
</DD>
<DT><EM>Key</EM></DT>
<DD>A key to set
</DD>
<DT><EM>Value</EM></DT>
<DD>The value corresponding to Key
</DD>
<DT><EM>Tree</EM></DT>
<DD>The tree after setting
</DD>
</DL>
<H2>Description</H2>
	<P>
	If the key Key already exists in the tree Tree0, then this predicate
	updates the corresponding value to be Value.  Otherwise it inserts
	the key Key into the tree with value Value.  The resulting tree is
	Tree.
	</P>
	<P>
	This predicate should only be called with trees created by other
	predicates from the tree234 module.
	</P>
	
<H3>Fail Conditions</H3>
Never fails.
<H3>Resatisfiable</H3>
no
<H2>See Also</H2>
<A HREF="../../lib_public/m_tree234/insert-4.html">insert / 4</A>, <A HREF="../../lib_public/m_tree234/update-4.html">update / 4</A>
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